[Improvement] add style guidance on delimiters used in lists

[jai]

What article on docs.github.com is affected?

https://github.com/github/docs/blob/main/contributing/content-style-guide.md

What part(s) of the article would you like to see updated?

There doesn't seem to be standardization on the delimiters to be used in lists with a 'key' and a 'value' - as mentioned in this comment

Some lists use a hyphen, whereas others use a colon. If this is mentioned somewhere in the style guide, I missed it. There doesn't seem to be anything in the Lists section.

https://docs.github.com/en/developers/webhooks-and-events/webhook-events-and-payloads#pull_request_review

https://docs.github.com/en/developers/webhooks-and-events/webhook-events-and-payloads#release